Methods and apparatus for evaluating insulating glass units

ABSTRACT

An apparatus and method for measuring the gas fill concentration of insulating glass units is disclosed. One apparatus includes a gas fill concentration measuring device coupled to a production line for manufacturing insulating glass units. One method of the invention involves measuring the gas fill concentration of insulating glass units after they have been filled with gas and sealed.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/875,640, filed Jun. 24, 2004, titled Methods and Apparatus forEvaluating Insulating Glass Units, which is a continuation of U.S.Patent Application 60/482,127, filed Jun. 24, 2003, titled InsulatedGlass Production Systems and Methods.

The entire disclosure of the above mentioned applications is herebyincorporated by reference.

FIELD OF THE INVENTION

The present disclosure relates generally to methods and devices forevaluating insulating glass units in a production environment and insitu. More particularly, the present disclosure relates to methods anddevices for evaluating the optical properties of insulating glass units.

BACKGROUND OF THE INVENTION

Insulating glass units (IGUs) are typically composed of two parallelglass panes spaced apart by a peripheral spacer. Spacers are typicallymade of metal, usually of tubular configuration, and are formed so as tohave two flat sides that face the confronting surfaces of the glasspanes. The spacers are bent so as to conform to the periphery of theglass panes. Typically, the spacers are adhered to the glass panes witha sealant that is gas-impermeable, such polyisobuytlene. An additionalsealant, with strong adhesion force, such as silicone, is commonlyapplied around the outside edges of the IGU. For aesthetic purposes,muntins may be sandwiched between the panes to give the unit a dividedlight appearance. To improve thermal resistance across the glassassemblies, the space between the panes of glass, or interpane space,may be filled with an insulating gas such as argon. To performadequately, the IGU must be filled with a proper amount of gas.Typically, the amount of gas flowed into the interpane space is gaugedby flowing gas at a known rate for a specified period of time into theIGU.

Often, at least one pane surface of an insulating glass unit is coatedwith a low energy coating to prevent conduction of heat through theglass. These coatings can result in the reflectance of color from theglass surface. Typically, color reflectance is undesirable. Therefore,for aesthetic purposes, it is desirable to manufacture glass and IGUsthat reflect at wavelengths in the blue or blue/green range.

In the manufacture of insulating glass units, uniform production linesare often used to produce large quantities of glass assemblies. In atypical production line, glass panes are transported to a conveyor withrollers on a vertical platen that transports the panes to a number ofstations where various steps of the assembly process are performed.

In terms of quality assuring the reflected color of a IGU, for example,the methods have generally involved measuring the transmitted color of acoated glass pane before it is assembled into an IGU. Similarly, the gasfill concentration is typically quality controlled by proceduresinvolving methods that destroy the IGU after the IGU has been fullyassembled and removed from the production line. Therefore, materials arewasted and each unit cannot be quality assured.

It would be desirable therefore, to provide a quality control methodthat is capable of quality assuring each IGU produced in anon-destructive manner. Furthermore, to reduce costs, it would bedesirable to provide an automated or semi-automated system on aproduction line that can quickly and accurately quality assure IGUs asthey are manufactured without sacrificing materials, time, and laborexpenses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an insulating glass unit.

FIG. 2 is a cross-sectional illustration of the insulating glass unitshown in FIG. 1.

FIG. 3 depicts a conveyer for use on an insulating glass unit productionline.

FIG. 4 is a schematic of a color measuring station on an insulatingglass unit production line according to an embodiment of the presentinvention.

FIG. 5 is an alternative embodiment of the color measuring station shownin FIG. 4.

FIG. 6 is a schematic of a gas fill concentration measuring station onan insulating glass unit production line according to an embodiment ofthe present invention.

FIG. 7 is a schematic of a dual color and gas fill measuring stationprovided on an insulating glass unit production line according to anembodiment of the present invention.

FIG. 8 illustrates the embodiment of FIG. 7 in operation.

FIG. 9 is a schematic diagram of an apparatus in accordance with anadditional exemplary embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 illustrates one example of an insulating glass unit (IGU) 10,that can be provided according with the present invention. It is to beunderstood that the invention is not limited to practice with anyparticular type of IGU. To the contrary, all aspects of the presentinvention can be practiced in connection with insulating glass units ofall types. Thus, the details of the illustrated IGUs should not beconstrued as limiting the scope of the present invention. Moreover, itis to be understood that, while the term insulating “glass” unit is usedthroughout the present disclosure, the panes 12 and 12′ may be formed ofmaterials other than glass for some applications.

The IGU 10 illustrated in FIG. 1 includes a first pane 12 and a secondpane 12′ together forming a pair of panes. The panes bound abetween-pane space (i.e., an “interpane space” or “gas space”) 14therebetween and an exterior space thereabout. The panes are preferablyspaced apart in a substantially parallel relationship by a spacer 18(illustrated in FIG. 2). In more detail, the peripheral inner surfacesof the panes are joined by the spacer 18. Thus, the spacer 18 and theconfronting inner surfaces of the panes 12, 12′ together define theinterpane space 14.

Typically, the spacer 18 is formed of a metallic tubing (e.g., aluminum,stainless steel and others). This tubing can be provided in a variety ofcross-sectional configurations. Examples of spacers that may be suitablein some applications are disclosed in U.S. Pat. Nos. 5,377,473;5,439,716; 5,679,419; 5,705,010, and 5,714,214, the entire teachings ofeach of which are incorporated herein by reference. It is also notedthat a variety of conventional spacer designs are commercially availablefrom Alumet Manufacturing, Inc., which is located in Marysville, Wash.,U.S.A.

Regardless of the particular spacer configuration, the spacercharacteristically includes two generally opposed lateral surfaces thatare adapted to be bonded respectively to the peripheral inner surfacesof the panes. Bonding the spacer to both panes desirably forms agas-tight seal that prevents air and other gases from entering and/orescaping the interpane space. The interior of the spacer desirablycarries a deposit of desiccant 19 (best shown in FIG. 2). The desiccant19 is preferably provided in a flowable form (e.g., in a granular orpowdered form), to facilitate flowing desiccant into the interior of thespacer. Desiccants of this nature are conventional in the present artand are available through a number of commercial suppliers.

The sealing system of an IGU 10 desirably minimizes gas flow between thegas space inside the unit and the ambient environment outside the unit.While some IG units have only a single seal, other IG units typicallyinclude two seals: a primary or “first” seal 22 and a secondary or“second” seal 24, better illustrated in the cross section of FIG. 2. Thefirst seal 22 is preferably formed of material that is resistant topermeation of air, moisture, and any insulative gas fill. For example,this seal can be advantageously formed of a butyl sealant (e.g.,polyisobutylene). The second seal 24 is preferably formed of materialthat has good adhesive properties. For example, this seal 24 can beformed of silicone, polysulfide, polyurethane, or any other materialthat bonds adhesively with the spacer and panes. Thus, the spacer 18,together with the first 22 and second 24 seals, isolates the gaseousatmosphere within the interpane space 14 from the ambient atmosphere ofthe exterior space.

The interpane space 14 of an IGU 10 can be advantageously filled with aninsulative gas. It is to be understood that the term insulative gas isused herein to refer to any gas that is a better thermal insulator thanair. For example, a gas is to be considered insulative if it has a lowerthermal conductivity than air, and hence reduces (relative to an IGUcontaining air) heat transfer by conduction. A gas is also to beconsidered insulative if it is heavier than air, and hence reduces(relative to an IGU containing air) heat transfer by convection. Forexample, argon is a preferred insulative gas since it is both lessthermally conductive and heavier than air. Other inert gas fills can beused as well. Argon, krypton, and other inert gases are commerciallyavailable from a number of suppliers, including BOC Gases (Murray Hill,N.J., U.S.A.), Air Products and Chemicals, Inc. (Allentown, Pa.,U.S.A.), and Air Liquide America Corporation (Cambridge, Md., U.S.A.).

IGUs of standard size can be assembled on IGU production or assemblylines. FIG. 3 illustrates generally a production line for manufacturingIGUs. Typically, if the IGU 10 is to comprise glass panes with acoating, the coating is applied to the panes prior to assembly of theIGU.

It is to be understood that the following description of an IGUproduction is illustrative only and the invention is not limited to useon a production line generally or to use on any particular productionline. The assembly line and assembly stations described herein may bevaried with the addition or deletion of various stations.

The glass panes are typically manually loaded onto a conveyor 26 thattransports the panes and partially assembled units to various stationsfor processing. The conveyor 26 may be comprised of a generallyhorizontal belt or other suitable solid surface to support the bottomsurface of the glass panes or partially assembled units. A generallyvertical platen 28 with a plurality of rollers 30 for vertical supportand propulsion of the panes or partially formed propels the glass panesor partially formed IGUs through the production line.

In an illustrative production line, for example, the glass panes may beconveyed to a variety of stations including, for example, an edgedeletion station where, if present, the coating on the glass is removedfrom the perimeter of the pane. The edge deleted glass pane may then beconveyed to a washing station to remove any debris or unwanted materialfrom the surface of the pane. A gas-impermeable sealant is applied tothe edges of a spacer dimensioned to the particular configuration of theIGU are adhered to the periphery of the one pane of a pair of panes.

Pairs of panes, one pane with a spacer adhered and a bare pane may benext conveyed to an assembly station (not shown) where the pairs aremated and joined together through the exposed primary sealant on theedge of the spacer opposing the edge adhered to the glass pane.

The partially assembled IGUs are then conveyed to a gas-fill stationwhere typically, an insulating gas is inserted into the interpane spaceand the unit is sealed. One exemplary mechanism for filling IGUs isdisclosed in U.S. Pat. No. 5,957,169, the entire disclosure of which ishereby incorporated by reference.

FIG. 4 illustrates a color measuring station 32 positioned downstreamfrom a gas fill station. After an IGU 10 is filled with gas and sealed,it is conveyed to the color measuring station 32 where the color of areflected light emission that has been transmitted through the glasspanes is measured. Alternatively, the IGUs may be manually transportedby personnel to the station 32.

A color change produced by the coated substrates of the IGU may bemeasured by using devices that transmit light that has a knownwavelength distribution over the visible spectrum. The light from thesource may strike the coated substrate at an angle that is generallyperpendicular to the surface of the substrate. A light detector maymeasure the light intensity at various wavelengths across the visiblespectrum and compare these measurements to the known wavelengthdistribution of the source to determine one or more opticalcharacteristics of a sample being evaluated

Color measuring station 32 of figure for comprises a color measuringdevice 34. Color measuring device 34 may comprise various instrumentswithout deviating from the spirit and scope of the present invention.Examples of instruments that may be suitable in some applicationsinclude calorimeters and spectrophotometers. For example, an apparatusin accordance with some embodiments of the present invention maycomprise various commercially available spectrophotometers. Onespectrophotometer that may be suitable for some applications iscommercially available from Minolta Camera company of Osaka, Japan whichidentifies it with the model number CM-2500D. Color measuringinstruments are described in a number of U.S. Pat Nos., including:4397533; 4402611; 4917495; 4995727; 5,168,155; 5214494; 5432609;5570192; 5592294; 5831740; 5859709; 5963334; 5978606; 6020959; 6088117;6462819; 6614518; and 6707553. The entire disclosure of each U.S. Patentlisted above is hereby incorporated by reference.

Color measuring device 34 can be coupled to the production line by anysuitable means. For example, as shown in FIG. 4, the color measuringdevice 34 may be attached to a manually or automated extendable arm 36provided adjacent to the conveyer 26. The extendable arm 36 may bemovable perpendicularly with respect to the surface of the IGU so thatthe color measuring device 34 moves towards the surface of a glass pane12 as the IGU enters the station 32 to facilitate the measurement. Theextendable arm 36 includes an engagement surface (not shown) forengaging and securing the IGU 10 during measurement. The engagingsurface should contact the glass surface and apply a pressure that issuitable for securing the unit without damaging the unit. A force ofabout 10 psi may serve both requirements in some applications. Tofurther protect the IGU, the engaging surface may be covered with a softmaterial, for example, felt, so that it does not damage the glasssurface.

In some embodiments of the present invention, a reflecting surface maybe provided on a surface opposing the detector. For example, areflecting tile 38 may be provided on the vertical platen 28 inalignment with the detector of the color measuring device 34.

FIG. 5 illustrates an alternative embodiment wherein the color measuringdevice 34 is attached to the vertical platen 28 and the reflecting tile38 is provided on the opposing side of the IGU 10, for example, byattachment to an extendable arm 36 or other structure.

Coatings are typically applied to the #2 surface of panes, which is theinterior surface of the pane of glass facing the exterior of thebuilding. The coating often results in the reflectance of color to theeye of an observer. Such coloration can be problematic and detract fromthe architectural beauty of a building. Generally, it is desirable toprovide IGUs that are aesthetically pleasing to people observing theexterior of the building into which the IGU is incorporated. Therefore,advantageously, in practicing the invention, according to anyembodiment, the glass sheets may be loaded onto the production line sowhen the IGU 10 reaches the color measuring station 32, the IGU 10 ispositioned so that the device for measuring color 34 detects thetransmitted color from the #2 surface through the #1 surface. In thisconfiguration, the color visible from the exterior of the building willbe monitored.

In operation, as an IGU 10 enters the station 32 it is positioned sothat a portion of the glass surface 12 is aligned with the colormeasuring device. The extendable member 36 moves towards the IGU 10 andcontacts the glass pane 12 closest to it with the soft surface (notshown). The extendable member 36 stabilizes the IGU 10 against thevertical platen 28 while the reading is made. The color measuring device34 emits radiation towards the IGU. This radiation travels through thepanes 12 and 12′ and space 14 until it reaches the tile 38. Theradiation striking the tile 38 is reflected back to a detector on thecolor measuring device 34 and the appropriate correlations are made.

FIG. 6 illustrates an alternative embodiment where a gas fillconcentration measuring device 40 is provided at a station 42 positioneddownstream from a gas fill station (not shown). The gas fillconcentration measuring device 40 measures the concentration of the gasin the interpane space in a fashion that does not compromise theintegrity of the assembled IGU. Use of a non-destructive method allowsfor each unit to be quality assured before it reaches the customer. Anexample of such a gas fill concentration device is the GasGlass-1001commercially available from Sparklike, Ltd., of Helsinki, Finland.

The gas fill concentration measuring device 40 may be secured to theproduction line in any matter suitable to bring it into proximity to theIGU 10 to be measured. For example, the device 40 may be attached to anextendable arm 36, similar to the color measurement device, providedadjacent to the production line. The extendable arm 36 may be movableperpendicularly with respect to the surface of a glass pane 12 of theIGU 10 so that it may move into proper position to take the reading.

When an IGU reaches the station, the extendable member 36 is activatedand moves toward the IGU 10 bringing the gas fill concentrationmeasuring device 40 into contact with the surface of the glass pane 12of the IGU 10. The gas fill concentration measuring device 40 mayinclude a means for engaging the glass surface, for example a suctioncup, so that a measurement may be initiated. After the measurement ismade, the IGU 10 is conveyed out the station 42 or alternatively, ismanually removed.

FIG. 7 illustrates an alternative embodiment where the station 46includes both a color measuring device 34 and a gas fill concentrationmeasuring device 40. The dual measuring station 46 is positioneddownstream from a gas fill station so that the IGUs are least partiallyassembled and filled with gas as they move through the production line.

The color measuring device 34 and gas fill concentration sensor 40 maybe mounted to an extendable arm 48 coupled to the conveyor 26 adjacentto the IGU 10. A reflecting tile 38 may be provided on the verticalplaten 28 in alignment with the color measuring device to facilitate themeasurement as previously described. The extendable arm 48 may includean engaging surface for contacting and stabilizing the IGU while themeasurements are taken.

In an alternative embodiment, the color measuring device is mounted tothe vertical platen 28 and a color reflecting tile 38 is mounted on theextendable member 48 in alignment with the color measuring device 34 andthe gas fill concentration sensor 40 is mounted on the extendable member48 (as described above).

FIG. 8 illustrates the embodiment of FIG. 7 in operation. When an IGU 10present on the conveyer 26 reaches the station 46, the conveyer 26 isstopped so that the measurements may be taken. The extendable arm 48carrying the color measuring device 34 and gas fill concentrationmeasuring device 40 is activated and moved toward the glass surface 12so that the engagement surface (not shown) contacts the glass surface.The extendable arm 48 may be moved in either the X or Y axis (of theglass pane surface) to avoid any obstructions, such as muntin bars. Oncethe positioning is satisfactory, the color measuring device 34 isactivated and the color reading taken. Next, the gas fill concentrationmeasuring device 40 is moved towards the glass pane surface 12 where thesuction cup or other suitable gripping means engages the glass surface12. The gas fill concentration measurement device is activated to take ameasurement. The measurements may be taken in various sequences. Forexample, the gas fill concentration may be measured first, oralternatively, both measurements may be taken simultaneously.

Positioning the station at a location downstream from the gas fillstation provides the advantage of measuring the gas fill concentrationand color of IGUs after complete assembly but before any maskingmaterial, which may interfere with measurements, is applied to the IGU.

Reductions in manual labor and time required necessary to produce IGUsis desirable as cost reducing measures. Providing a dual color and gasfill measuring station on the IGU production line allows for efficient,time effective manufacture and quality assurance. Both the reflectedcolor and gas fill can be evaluated at a single stop, reducingproduction costs by automating quality assurance procedures and reducingthe time required to carry out the procedure. The stop period, that is,the time an IGU will spend at the color and gas fill concentrationcenter, is preferably less than 30 seconds and more preferably is in therange of 10-20 seconds.

The data obtained from the measuring devices according to any embodimentdescribed herein, can be captured and transmitted to a database 50. Themeasuring devices 34 and 40 may be coupled to the data base 50, forexample, a personal computer or alternatively the data may betransmitted telemetrically. The stored data can be used for a variety ofpurposes. For example, stored data can be used for quality control tomonitor the retention of gas within the IGU. The gas concentration of anIGU can be measured at any time subsequent to manufacture and comparedagainst the concentration at the time of manufacture to determinewhether the IGUs are properly retaining the gas. The stored data may beused for a variety of other purposes as is appreciated by the skilledartisan.

FIG. 9 is a schematic diagram of an apparatus 52 for evaluating aninsulating glass unit 54. Insulating glass unit 54 comprises a firstpane 56, a second pane 58 and a spacer 60 interposed between first pane56 and second pane 58. First pane 56, second pane 58, and spacer 60define an interpane space 62. Apparatus 52 comprises a color measuringdevice 64 and a gas fill concentration measuring device 66. Colormeasuring device 64 comprises a first controller 68, a first lightsource 70 and a first photosensor 72.

As shown in FIG. 9, first light source 70 of color measuring device 64is disposed outside of interpane space 62 of insulating glass unit 54. Afirst light emission 78 produced by first light source 70 is illustratedusing arrows in FIG. 9. In FIG. 9, light from first light emission 78 isshown traveling in a first direction 84 as it passes through first pane56 and second pane 58 before striking a reflective tile 86. Also in FIG.9, light from first light emission 78 is shown traveling in a seconddirection 82 as it passes through second pane 58 (a second time) andfirst pane 56 (a second time) before striking first photosensor 72.

First light source 70 may comprise various light sources withoutdeviating from the spirit and scope of the present invention. In theembodiment of FIG. 9, first light source 70 comprises a xenon flash lamp88. It is also important to note that reflective tile 86 may comprisevarious reflective surfaces without deviating from the spirit and scopeof the present invention. In some implementations, for example,reflective tile 86 may comprise a white surface.

In the embodiment of FIG. 9, gas fill concentration measuring device 66comprises a second controller 75 and a second photosensor 76 that iscapable of sensing light from a second light emission 80. In theembodiment of FIG. 9, light from a second light emission 80 is carriedto second photosensor 76 by a fiberoptic cable 90. It is important tonote that various embodiments of first photosensor 72 and secondphotosensor 76 are possible without deviating from the spirit and scopeof the present invention. In some embodiments, for example, thesephotosensors may comprise a plurality of filters having differentspectral transmittances and a plurality of photodiodes that are arrangedto be illuminated by light that has passed through selected filters.

In FIG. 9, second light emission 80 is produced by a plasma 92 that isdisposed within interpane space 62 of insulating glass unit 54. Plasma92 may be identified as a second light source 74. In the embodiment ofFIG. 9, gas fill concentration measuring device 66 comprises a fieldgenerator 94 that is capable of exciting a gas 98 disposed in interpanespace 62 to form plasma 92. Also in the embodiment of FIG. 9, generator94 is capable of generating an oscillating magnetic and/orelectromagnetic field proximate an outer surface 96 of insulating glassunit 54.

Generators are described in a number of U.S. Pat. Nos., including:5,303,139; 6,538,388; 6,567,278; 6,586,887; 6,727,654; 5,712,592; and6,750,614. The entire disclosure of each U.S. Patent listed above ishereby incorporated by reference.

In the embodiment of FIG. 9, both color measuring device 64 and gas fillconcentration measuring device 66 are connected to a computer 100.Computer 100 may comprise various elements without deviating from thespirit and scope of the present invention. Examples of elements that maybe suitable in some applications include a personal computer, amicroprocessor, and a microcontroller.

In the embodiment of FIG. 9, color measuring device 64 is shownproviding a first signal 102 to computer 100 and gas fill concentrationmeasuring device 66 is shown providing a second signal 104 to computer100. First signal 102 may be, for example, representative of lightsensed by first photosensor 72 from first light emission 78. Secondsignal 104 may be, for example, representative of light sensed by secondphotosensor 76 from second light emission 80.

In some embodiments of the present invention, computer 100 may decide toaccept or reject insulating glass unit 54 based upon both first signal102 and second signal 104. For example, computer 100 may be capable ofcomparing first signal 102 with a first acceptable range and comparingsecond signal 104 with a second acceptable range. Computer 100 may thengenerate a reject signal if first signal 102 is outside the firstacceptable range or if second signal 104 is outside the secondacceptable range.

In some embodiments of the present invention, computer 100 may becapable of correcting second signal 104 to compensate for a color changethat occurs in second light emission 80 as it passes through a singlepane of insulating glass unit 54. For example, computer 100 may use acolor change that occurs in light from first light emission 78 as itpasses through first pane 56 and second pane 58 a first time and asecond time. The color change may be calculated by comparing a knowncolor of light emitted by first light source 70 to the color of lightreceived by first photosensor 72. This comparison may include addingand/or subtracting color components. The color of light received bysecond photosensor 76 may be determined from second signal 104. Onequarter of the color change may be subtracted from and/or added to thecolor of light received by second photosensor 76 to correct for a colorchange that occurs in second light emission 80 as it passes through asingle pane of insulating glass unit 54.

While a preferred embodiment of the invention has been disclosed, itshould be understood that various changes, adaptations, andmodifications may be made therein without departing from the spirit ofthe invention and the scope of the appended claims.

1. A system for producing insulating glass units in a production lineenvironment, the system comprising: a conveyer for transportingcomponents that form the insulating glass units as well as theinsulating glass units themselves to stations located along theproduction line; a gas fill concentration measuring device located at astation of the production line wherein the device measures the gas fillconcentration of an insulating glass unit delivered to that station andgenerates a signal based on a gas fill concentration measurement; and acomputer configured to receive the signal generated by the device and todecide whether to accept or reject the insulating glass unit based uponthe signal.
 2. The system of claim 1, further comprising an extendablemember located at the station with the device wherein the extendablemember contacts and secures the insulating glass unit while the gas fillconcentration is measured.
 3. The system of claim 1, wherein the gasfill concentration sensor is coupled to the extendable member.
 4. Thesystem of claim 1, wherein the extendable member is movable in at leastthe X or Y axis relative to the insulating glass unit.
 5. The system ofclaim 1, wherein the gas fill concentration sensor operates during asingle stop period.
 6. The system of claim 5, wherein the stop period isin the range of 10-20 seconds.
 7. The system of claim 1, wherein thedevice, comprises: a means for emitting a light emission from within theinterpane space of the insulating glass unit; and a photosensor forsensing light from the light emission that has passed through at least aportion of the insulating glass unit.
 8. The system of claim 7, whereinthe means for emitting a light emission from within the interpane spaceof the insulating glass unit comprises a field generator for exciting agas disposed in the interpane space to form a plasma.
 9. The apparatusof claim 8, wherein the generator is configured to generate anoscillating magnetic field proximate an outer surface of the insulatingglass unit.
 10. The system of claim 7, wherein the signal is based onlight sensed by the photosensor from the light emission.
 11. The systemof claim 10, wherein the computer is configured to: compare the signalwith an acceptable range; and generate a reject signal if the signal isoutside the acceptable range.
 12. The system of claim 10, wherein thecomputer is configured to: compare the signal with an acceptable range;and generate an accept signal if the signal is within the acceptablerange.
 13. The system of claim 10, wherein the computer is configured tocorrect the signal to compensate for a color change occurring in lightfrom the light emission as that light passes through a single pane ofthe insulating glass unit.
 14. A method for measuring gas fillconcentration of insulating glass units during manufacture thereof, themethod comprising the steps of: conveying a gas-filled insulating glassunit to a gas fill concentration measuring station to obtain a gas fillmeasurement; measuring the gas fill concentration of the insulatingglass unit at the gas fill concentration measuring station, determiningwhether the gas fill concentration measurement is within an acceptablerange; and accepting or rejecting the insulating glass unit.
 15. Themethod of claim 14, further comprising the step of transmitting gas fillconcentration data to a database for storage.
 16. The method of claim14, further comprising the steps of: coupling two panes of glasstogether to create an interpane space therebetween; filling theinterpane space with insulating gas to produce a partially formedinsulating glass unit; measuring gas fill concentration of the partiallyformed insulating glass unit at a station on a production line,determining whether the gas fill concentration is within an acceptablerange; accepting or rejecting the insulating glass unit.
 17. The methodof claim 16, further comprising transmitting gas fill concentration datato a data base for storage.
 18. A method for evaluating an insulatingglass unit comprising the steps of: emitting a light emission from alight source disposed within an interpane space of the insulating glassunit; sensing light from the light emission that has passed through atleast a portion of the insulating glass unit; generating a signal basedon the light sensed from the light emission; providing the signal to acomputer configured to determine whether light sensed from the lightemission is within acceptable ranges; and accepting or rejecting theinsulating glass unit.
 19. The method of claim 18, wherein the step ofsensing light from the light emission that has passed through at least aportion of the insulating glass unit comprises the step of sensing lightfrom the light emission that has passed through a single pane of theinsulating glass unit.
 20. The method of claim 18, wherein the lightsource comprises a plasma.
 21. The method of claim 18, wherein the stepof emitting a light emission from the light source comprises the step ofexciting a gas disposed in the interpane space to form a plasma.
 22. Themethod of claim 21, wherein the gas disposed in the interpane spacecomprises argon.
 23. The method of claim 21, wherein the step ofexciting the gas disposed in the interpane space comprises the step ofgenerating an oscillating magnetic field proximate an outer surface ofthe insulating glass unit.
 24. The method of claim 18, further includingthe step of deciding whether to accept the insulating glass unit basedupon the signal.
 25. The method of claim 18, further including the stepsof: comparing the signal with an acceptable range; and generating areject signal if the signal is outside the acceptable range.
 26. Themethod of claim 18, further including the steps of: comparing the signalwith a second acceptable range; and generating an accept signal if thefirst signal is within the first acceptable range.
 27. The method ofclaim 18, further including the step of correcting the signal tocompensate for a color change occurring in light from the light emissionas the light passes through a single pane of the insulating glass unit.28. The method of claim 27, wherein the step of correcting the signalcomprises the step of calculating a color change that occurs in lightfrom the first light emission as it passes through at least a portion ofthe insulating glass unit.